1. Field of the Invention
The present invention relates generally to a method and system for allocating multiple channels in a mesh network. More particularly, the present invention relates to a method and system for allocating multiple channels between nodes which each have a single interface.
2. Description of the Related Art
Today, mobile communication technology is being developed toward maximization of transmission rate and frequency use efficiency in order to provide multimedia service. A major example is a mobile access network. The mobile access network refers to a network that provides high-speed wireless service to terminals within predetermined service coverage.
A traditional mobile access network is a set of local networks which each include Access Points (APs) and legacy Stations (STAs). A legacy STA receives an intended wireless service by association with an AP.
The mobile access network has recently evolved to a mesh network which combines a plurality of local networks. The mesh network is comprised of a plurality of nodes called Mesh Points (MPs). The MPs function as APs in local networks and directly exchange information with neighboring APs by association.
In the mesh network, communication is typically conducted between nodes via a single channel as illustrated in FIG. 1 or via multiple channels as illustrated in FIG. 2. In the former case, when a neighbor node uses a single channel, another node that the neighbor node may interfere with cannot use the channel. In the latter case, communications can be conducted between nodes simultaneously within an allowed number of channels.
FIG. 3 is a diagram illustrating a signaling procedure for data transmission between nodes which each have a single interface in a conventional mesh network supporting multiple channels. Data transmission is performed on a first channel (Channel 1) between a first node (Node #1) and a second node (Node #2) and on a second channel (Channel 2) between a third node (Node #3) and a fourth node (Node #4).
Referring to FIG. 3, channels are established during a beacon interval in the mesh network. The beacon interval is divided into an Ad-hoc Traffic Indication Message (ATIM) window and a data transmission interval. Within the ATIM window, a common channel is set up and during the data transmission interval, a selected channel is set up.
FIG. 4 is a diagram illustrating a signal flow between nodes during a data transmission interval in the conventional mesh network. Node #3 attempts to communicate with Node #2 which is communicating with Node #1. Therefore, Node #1 and Node #2 initially use the same channel and Node #3 uses a different channel.
Referring to FIG. 4, in the presence of transmission data, Node #1 broadcasts a Request to Send (RTS) message in step 410. Upon receipt of the RTS message, Node #2 broadcasts a Clear to Send (CTS) message in step 412.
Upon receipt of the CTS message, Node #1 sends data to Node #2 in step 414. Node #2 then replies to the data transmission with an acknowledgement (ACK) signal.
Meanwhile, Node #3 listens to a different channel from that of Node #1 and Node #2 has no knowledge of the situations of Node #1 and Node #2. When Node #3 needs to send data, it switches to a channel for communicating with a neighbor node and sends an RTS message in steps 416 and 418. If Node #3 switches to the channel in use for Node #1 and Node #2, a serious interference occurs. This is called a “Hidden Terminal Problem” which is encountered when multiple channels are used.
Accordingly, there is a need for an improved system and method to allocate multiple channels to solve hidden terminal problems between MPs which each have a single interface.